The following abbreviations are herewith defined, at least some of which are referred to within the following description of the state-of-the-art and the present invention.
3GPP3rd Generation Partnership ProjectAFApplication FunctionARPAllocation and Retention PriorityBSRBearer Setup RequestDSDynamic SchedulingEPS Evolved Packet SystemGBRGuaranteed Bit RateHSSHome Subscriber ServerIMS IP Multimedia SubsystemIPInternet ProtocolIP-CANIP Connectivity Access NetworkLTELong Term EvolutionMBMSMultimedia Broadcast and Multicast ServiceMBRMaximum Bit RateMMEMobility Management EntityPCRFPolicy and Charging Rule FunctionPDN-GWPacket Data Network GatewayPSPersistent SchedulingPTTPush to TalkRRCRadio Resource ControlQCIQoS class identifierQoSQuality of ServiceSPSSemi-Persistent SchedulingSRService RequestTFTTraffic Flow TemplateUEUser EquipmentURIUniform Resource IdentifierVoIPVoice over IP
Wireless communication networks are, as a matter of necessity, structured somewhat differently than their wireline, or POTS (plain old telephone service) predecessors. In general, a wireline system involves a large number of telephones, one or more of which each belong to a different subscriber. The phone or phones belonging to each subscriber are connected by a pair of wires to a switch located, for example, in a central office. When a call from one of these phones is placed, the central office sets up a circuit from the calling party through a variety of interconnected switches arranged in a hierarchical topology to the called party. The circuit remains in place until the call is completed, and then the network resources are freed for use by others.
In a wireless network, generally-speaking, base stations are installed in various geographic locations across a network-coverage area. Base stations are equipped with antennas and radio transceivers to communicate over an air interface with mobile telephones and other devices that are within range. Because each base station only communicates with mobile devices in their vicinity, transmission power for both the base station and the mobile device can be kept relatively low. In addition to reducing the power requirements for portable (and often battery-powered) mobile devices, this also allows for radio communications using the same frequencies by other base stations and mobile devices not in the immediate vicinity.
A mobile device may make or receive calls via a nearby base station. In either case, as a communication session is being initiated the base station assigns certain bearer resources that are expected to be needed for the call. A bearer resource is a communication channel or channels for carrying uplink communication traffic from the mobile device to the base station and downlink traffic from the base station to the mobile device. Resources are reserved when a communication session is set up to ensure that the quality of the anticipated call may be preserved. (Other channels may be reserved for control signaling.) A reserved channel may be a single radio frequency, but in many cases this single radio frequency may be shared with other communication sessions, for example by assigning certain time slots on that frequency to each session. Various scheduling routines are used to allocate time slots for transmission. Calls that cannot be satisfactorily accommodated are usually not set up. A reserved bearer resource may be released when the session has been terminated or when the mobile device relocates and continues the communication session using another base station.
As might be apparent, base stations, which may communicate with a large number of nearby mobile devices, are typically fixed in one location. From there they are connected to a network that allows communications to a great many other devices, for example wireless devices communicating through other base stations, or via a gateway device with telephones and other devices that are associated with different networks.
Another difference between many modern wireless networks and traditional POTS networks is that network communications may be effected using packet switching technology rather than by a dedicated circuit. (Although note that some wireline access networks may use packet switching as well.) In packet switching, information, including data representing the sounds of a voice communication, is divided into discrete data segments such as packets or frames. These packets are individually addressed and transmitted over a series of network nodes until they reach their destination, where they are reassembled to reproduce the transmitted data. In VoIP (voice over Internet Protocol), for example, this is done rapidly enough to enable the transmission of coherent voice conversations.
One service that may be offered by wireless networks is group calls. Here, two or more parties with appropriately-equipped mobile devices may effectively set up a multi-party communication session. In this session, a voice communication enunciated by one party is transmitted to all members of the group. Other members of the group may then speak in turn; network protocols are in place to govern whose turn it is speak. For example, any group member may request “the floor” by sending a request. In many systems, this involves pressing a key on the mobile device, and the service is sometimes referred to as “push-to-talk” (PTT). In any event, when the floor is granted, the requester is normally allowed to transmit to the other group members until the floor is released, for example by releasing the PTT button. If another group member requests the floor when it has been allocated already, their request is usually denied and they must wait and try again at a later time. The exact rules for permitting transmissions to the group may of course vary from one network to another.
In a broadband wireless network PTT environment, each user communicates with the network as if they were making or receiving a call. That is, a communication bearer is established between each nearby group member and the appropriate bearer resources are allocated. Each group member then in effect in involved with a communication session, usually with a PTT server of some kind that may be accessed through the wireless network and a packet data network via a PDN-GW. The PTT server then allocates speaking time (“the floor”) according to the rules that are in place, and actually handles the task of transmitting received group transmissions to the appropriate group members. The base station, such as the eNodeB in an LTE network, is unaware that the call is a group call and simply handles communications between the PTT server and the UE as if they were each individual voice calls.
Network resources such as the bearer resources over the air interface used by members of a talk group are valuable, and sometimes scarce. Plentiful or even adequate resources can frequently be guaranteed only by a greater infrastructure implementation. Providing inadequate resources results in customer dissatisfaction and in some cases more serious consequences. PTT group call may, for example, be used by first responders and emergency workers to aid persons and property in immediate danger. Naturally, refusing to set up a group call under such circumstances could be disastrous. A manner of more efficiently allocating broadband wireless network resources in the PTT environment is therefore needed.
Accordingly, there has been and still is a need to address the aforementioned shortcomings and other shortcomings associated with group call admission control. These needs and other needs are satisfied by the present invention.